Low temperature heat source usually refers to heat sources below 200.degree. C. There are a variety and a huge amount of low temperature heat sources, mainly including solar energy, geothermal energy and industrial waste heat etc. According to statistics, the solar radiation of two-thirds of the whole land area in China is greater than 5000 MJ per square meter, the amount of recoverable geothermal resources in the country is about 3.3 billion tons of standard coal, and the industrial energy consumption accounts for 70 percentage of the total energy consumption, while the industrial waste heat consumption accounts for 15 percent of the total energy consumption. Since the low temperature heat sources are difficult to be utilized by conventional energy conversion devices, most of these energies are discharged into the environment, causing great waste and environmental pollution. Therefore, how to recycle this part of huge amount of energy efficiently becomes a hot topic in the field of energy technology. The organic Rankine cycle power generation system uses low-boiling working fluid, the working fluid steam can flow into the turbine for expansion with a higher pressure, the device has simple structure, feasible technology and high energy efficiency, compared with the traditional steam Rankine cycle power generation system, the organic Rankine cycle power generation system is more suitable to use these low temperature heat sources.
As early as 1924, the scientists began to study the organic Rankine cycle using the low-boiling organic working fluid such as ether. With awareness of worldwide energy crisis increasing, governments and energy scientists focus on organic Rankine cycle technology. The United States, Japan, Israel, Italy, Germany, France and other countries have been devoted a lot of manpower and resources to competing on research and development of organic Rankine cycle power generation technology. At present, the organic working fluid of the Rankine power system is mainly applied in geothermal power plants, solar energy, industrial waste heat and biomass thermal power generation. The companies mastering organic Rankine cycle power generation technology mainly include Electra Therm, Turboden, Eneftech, Ormat, Freepower, Green Energy Australasia and Infinity turbine etc all over the world. The development of organic Rankine cycle power generation technology and system in China began in the early 1970s. Although organic Rankine cycle power generation technology has been developed over years, China is technically not been able to achieve substantial breakthroughs.
The conventional organic working fluid generation method has to work with external power. The working fluid need to be pressured by the pump to maintain normal power state, while the working fluid pump itself needs to consume a lot of power, resulting in reduced overall system efficiency. In addition, the control process also requires externally supplied power. So the conventional organic Rankine cycle power generation system largely depends on external power and needs equipment maintenance costs.